The present disclosure relates to a horizontal-electric field liquid crystal display panel. More specifically, the invention relates to a Fringe-Field-Switching (referred to as “FFS” in the following description)-mode liquid crystal display panel with good viewing-angle characteristics and with less coloring.
As the liquid crystal display is characterized in that it is light in weight, thin, and has low power consumption as compared with a CRT (cathode ray tube), it is used for many electronic apparatus for display. The liquid crystal display panel changes orientation of liquid crystal molecules by an electric field, which are aligned in a given direction by performing rubbing processing to an alignment film, and changes the transmission amount or the reflection amount of light to display images.
As methods for applying an electric field on a liquid crystal layer of the liquid crystal display panel, there are a vertical-electric field type and a horizontal-electric field type. In a vertical-electric field liquid crystal display panel, an electric field of a nearly vertical direction is applied to liquid crystal molecules by a pair of electrodes arranged so as to sandwich the liquid crystal layer. As the vertical-electric field liquid crystal display panels, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, a MVA (Multi-domain Vertical Alignment) mode and the like are known. In a horizontal-electric field liquid crystal display panel, a pair of electrodes are provided so as to be insulated from each other on an inner surface of one of a pair of substrates arranged to sandwich the liquid crystal layer and an electric field of a nearly horizontal direction is applied to liquid crystal molecules. As the horizontal-electric field liquid crystal display panels, an IPS (In-Plane Switching) mode in which the pair of electrodes do not overlap in plan view and an FFS (Fringe Field Switching) mode in which the pair of electrodes overlap are known.
Among the above modes, in the FFS-mode liquid crystal display panel, a pair of electrodes including an upper electrode and a lower electrode are arranged at different layers respectively through an insulating film, slit-shaped openings are provided at the upper electrode and the electric field in the nearly horizontal direction passing through the slits is applied to the liquid crystal layer. The FFS-mode liquid crystal display panel is widely used in recent years because it has advantages such that wide viewing angle can be obtained as well as image contrast can be improved. However, a slit having a fixed width is used in each sub-pixel in the horizontal-electric field liquid crystal display panel, therefore, there are a problem that coloring occurs depending on a viewing angle direction due to VT characteristics in respective sub-pixels. In order to improve the viewing angle characteristics and to reduce the coloring in the horizontal-electric field liquid crystal display panel, attempts to divide a rubbing direction into plural directions in one pixel have been made (refer to JP-A-2005-196118 (Patent Document 1)). Here, the liquid crystal display panel disclosed in Patent Document 1 will be explained in reference to FIG. 10.
FIG. 10 is a schematic plan view of one sub-pixel of the horizontal-electric field liquid crystal display panel disclosed in JP-A-2005-196118 (Patent Document 1).
In a horizontal-electric field liquid crystal display 50, one sub-pixel is divided into four domains of IA, IIA, IIIB, and IVB, and angles made by common electrodes 51a, 51b as well as pixel electrodes 52a, 52b driven by a TFT and rubbing directions are changed in respective domains. In the liquid crystal display panel 50, the four domains are formed by arranging the common electrodes 51a, 51b and the pixel electrodes 52a, 52b so as to be folded in the horizontal direction and the vertical direction respectively, the rubbing direction is changed in a region A and a region B of one sub-pixel, and further, color conversion is compensated with one another in respective domains to reduce the coloring.